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( σ , τ ) -derivations on prime near rings

Mohammad Ashraf, Asma Ali, Shakir Ali (2004)

Archivum Mathematicum

There is an increasing body of evidence that prime near-rings with derivations have ring like behavior, indeed, there are several results (see for example [1], [2], [3], [4], [5] and [8]) asserting that the existence of a suitably-constrained derivation on a prime near-ring forces the near-ring to be a ring. It is our purpose to explore further this ring like behaviour. In this paper we generalize some of the results due to Bell and Mason [4] on near-rings admitting a special type of derivation...

A classification of rational languages by semilattice-ordered monoids

Libor Polák (2004)

Archivum Mathematicum

We prove here an Eilenberg type theorem: the so-called conjunctive varieties of rational languages correspond to the pseudovarieties of finite semilattice-ordered monoids. Taking complements of members of a conjunctive variety of languages we get a so-called disjunctive variety. We present here a non-trivial example of such a variety together with an equational characterization of the corresponding pseudovariety.

A co-ideal based identity-summand graph of a commutative semiring

S. Ebrahimi Atani, S. Dolati Pish Hesari, M. Khoramdel (2015)

Commentationes Mathematicae Universitatis Carolinae

Let I be a strong co-ideal of a commutative semiring R with identity. Let Γ I ( R ) be a graph with the set of vertices S I ( R ) = { x R I : x + y I for some y R I } , where two distinct vertices x and y are adjacent if and only if x + y I . We look at the diameter and girth of this graph. Also we discuss when Γ I ( R ) is bipartite. Moreover, studies are done on the planarity, clique, and chromatic number of this graph. Examples illustrating the results are presented.

A fully equational proof of Parikh’s theorem

Luca Aceto, Zoltán Ésik, Anna Ingólfsdóttir (2002)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

We show that the validity of Parikh’s theorem for context-free languages depends only on a few equational properties of least pre-fixed points. Moreover, we exhibit an infinite basis of μ -term equations of continuous commutative idempotent semirings.

A Fully Equational Proof of Parikh's Theorem

Luca Aceto, Zoltán Ésik, Anna Ingólfsdóttir (2010)

RAIRO - Theoretical Informatics and Applications

We show that the validity of Parikh's theorem for context-free languages depends only on a few equational properties of least pre-fixed points. Moreover, we exhibit an infinite basis of μ-term equations of continuous commutative idempotent semirings.

A graph associated to proper non-small ideals of a commutative ring

S. Ebrahimi Atani, S. Dolati Pish Hesari, M. Khoramdel (2017)

Commentationes Mathematicae Universitatis Carolinae

In this paper, a new kind of graph on a commutative ring is introduced and investigated. Small intersection graph of a ring R , denoted by G ( R ) , is a graph with all non-small proper ideals of R as vertices and two distinct vertices I and J are adjacent if and only if I J is not small in R . In this article, some interrelation between the graph theoretic properties of this graph and some algebraic properties of rings are studied. We investigated the basic properties of the small intersection graph as diameter,...

A note on finitely generated ideal-simple commutative semirings

Vítězslav Kala, Tomáš Kepka (2008)

Commentationes Mathematicae Universitatis Carolinae

Many infinite finitely generated ideal-simple commutative semirings are additively idempotent. It is not clear whether this is true in general. However, to solve the problem, one can restrict oneself only to parasemifields.

A note on orthodox additive inverse semirings

M. K. Sen, S. K. Maity (2004)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

We show in an additive inverse regular semiring ( S , + , · ) with E ( S ) as the set of all multiplicative idempotents and E + ( S ) as the set of all additive idempotents, the following conditions are equivalent: (i) For all e , f E ( S ) , e f E + ( S ) implies f e E + ( S ) . (ii) ( S , · ) is orthodox. (iii) ( S , · ) is a semilattice of groups. This result generalizes the corresponding result of regular ring.

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